STOCKHOLDERS' EQUITY - Issuance of common stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018
Issuance of stock
Proceeds from issuance of common stock, net of issuance costs			$ 134,704	$ 99,765
Common Stock
Issuance of stock
Shares issued (in shares)			5,134,750	6,900,000
Common Stock | IPO
Issuance of stock
Shares issued (in shares)		6,900,000
Share price (in dollars per share)		$ 16.00
Gross Proceeds From Issuance Of Shares		$ 99,507
Proceeds from issuance of common stock, net of issuance costs		$ 10,900
Common Stock | Secondary Public Offering
Issuance of stock
Shares issued (in shares)	5,134,750
Share price (in dollars per share)	$ 28.00
Gross Proceeds From Issuance Of Shares	$ 134,704
Proceeds from issuance of common stock, net of issuance costs	$ 9,100